Bees Lured to Flowers by Exquisite 3D Iridescent Petal Patterns
There is a lot of competition in the natural world, so flowers have evolved to be clever, crafty, and cunning in figuring out how to lure bees and other pollinators to them.
University of Cambridge researchers have demonstrated that plants use buckling to alter the deformation of the surface of petals in hibiscus flowers, thereby gaining an advantage. Their findings were just published in Cell Reports.
What is buckling? It is a term used in structural engineering when beams and columns weaken and give way to mechanical failure. It is a dirty word and engineers wish to avoid it at all costs.
Buckling is not a term usually used in the world of plants and insects. In this case, flowers engage in materials science phenomenon to produce exquisite three-dimensional petal patterns that lure pollinators.
This unrelated 42:11-minute video by New Phytologist Foundation is far longer than we normally post, but is of interest to this topic:
There are several strategies flowers usually engage in to lure pollinators. One of these strategies is chemical color from pigments. Iridescence could be just as important for attracting bees and other pollinators, according to recent research.
It is unknown how plants develop the ridges, but this optical effect is produced by an intricate pattern of nano-scale ridges on the surface of petals that diffract light to cause iridescence. Like the shiny surface of CDs or glistening soap bubbles.
Dr. Sarah Robinson in the University of Cambridge's Sainsbury Laboratory, who led the research, worked with members of Professor Beverley Glover’s team, which was the first to discover the iridescence properties in flowers. The team suspected that the petal striations on hibiscus flowers develop during petal growth and may be caused by mechanical properties as the petals expand.
Dr. Robinson and Professor Glover's team tested this model by using a robotic system, called ACME (automated confocal micro-extensometer) that she had developed previously to measure mechanical properties in plants. They applied a specific force to stretch immature hibiscus (Hibiscus trionum) petals that had not yet developed striations to see if they could mechanically induce the patterns. According to Dr. Chiara Airoldi, the University of Cambridge’s Department of Plant Sciences and first author, the ACME developed by Dr. Sarah Robinson gave them the unique chance to investigate whether hibiscus striation patterns could be mechanically induced.
Striations appeared very quickly when a mechanical stress was applied. Dr. Robinson said this told them that buckling was causing a wrinkling of the petal surface instead of a slower biological process. They measured the striations and it showed they had the same properties as when they develop naturally. A big surprise was that they could induce striations at 90 degrees to the striations that naturally occur. This indicates that striation orientation is not pre-patterned. They were unable to induce striations in other parts of the petals, which implies the ability to form striations is genetically controlled.
The buckling happens in the cuticle, a waxy surfaced covering made up of two layers with different mechanical properties. This makes buckling possible.
What does all this mean? It means flowers are highly intelligent. They strategize and figure out how to survive. That is super cool! You can read the full research report and check out the illustrations, photos, and the amazing video by Dr. Sarah Robinson of the striations actually appearing before your eyes, here.
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